Hi.
My environment has 2x TMG 2010 std servers (TMG A and TMG B for this discussion) with the latest service pack and rollup and one exchange server behind them. Only TMG A has smtp inbound published. A recent issue I found is that sometimes email with an attachment from external fails with the following error:
4.4.2 Connection dropped due to SocketError
or
Last Error: 421 4.4.2 Connection dropped due to ConnectionReset
I then published smtp on the second server and the email goes through fine. After three days of testing I found that by disabling the NIS service on TMG A it allows the email to go through. My server sending me the email via the internet is not on any sbl list nor is my server receiving the mail.
My question is how can I find out which specific filter in NIS is causing this failure?
additional info.
tmg log states the following:
Status: A non-SYN packet was dropped because it was sent by a source that does not have an established connection with the Forefront TMG computer.
Source: ExternalDestination: Local Host
What I don't understand is why it is trying to communicate with the local tmg server when the rule is published to allow it an inbound connection to the mail server.
It is clearly a problem with the TMG A server as the TMG B server is allowing the mail through.
Best Regards, Morris Fury AFRIDATA.net